1. Field of the Invention
The present invention relates to a multispindle-head machine tool for bringing one of a plurality of multispindle heads into a machining position and operating an actuator unit to drive a plurality of tools of the multispindle head in the machining position.
2. Description of the Related Art
Multispindle-head machine tools having a plurality of multispindle heads each with a plurality of tools for simultaneously effecting different machining processes have heretofore been in widespread usage. In order to machine various different workpieces, a known multispindle-head machine tool has a plurality of multispindle heads, and a desired one of the multispindle heads is put in a machining position to machine the workpieces simultaneously. Since the multispindle heads are usually fed in a horizontal circulatory feed passageway, the multispindle-head machine tool is considerably large in overall size.
Japanese utility model publication No. 58-52003, for example, discloses an apparatus which has a turret head rotatable about a support shaft that is inclined 45.degree. to the horizon. The turret head has a plurality of tool head rests each supporting a multispindle head mounted thereon. When the turret head is angularly moved a certain angle, one of the multispindle heads is positioned in a horizontal machining attitude while the other multispindle heads are positioned in a vertical exchanging attitude.
In the known multispindle-head machine tool, a desired multispindle head has to be removed from the circulatory feed passageway along which the multispindle heads are successively fed, and to be installed on an actuator which is located at the machining position. Therefore, the process of exchanging multispindle heads is complex, lowering the efficiency of the machine tool especially when many different machining processes are required to be carried out on workpieces.
According to the above publication, the multispindle heads are successively oriented from the horizontal direction to the vertical direction as the turret head rotates. Therefore, if chips or a machining fluid produced in a machining process is applied to the multispindle head in the machining position, then the chips or the machining fluid tends to enter the multispindle head after the machining process. This is because when the tools stop rotating, the internal pressure of the multispindle head decreases as the temperature drops, tending to draw in the machining fluid applied to external spindles through seals of the spindles. As a result, the lubricant oil in the multispindle head is mixed with the introduced machining fluid.
If chips are applied to tools of the multispindle heads, then workpieces may suffer machining failures because of the chips when they are machined by these tools.
A jig table for holding workpieces is reciprocally movable along a horizontal plane on a column. Chips and a machining fluid are liable to be applied to the jig table, and the machining fluid finds its way into sliding areas in a linear guide and a rotary table, tending to adversely affect the lubricant oil.
According to the above publication, furthermore, a pair of arms on a multispindle head changer turns 180.degree. while gripping tool heads above the machine tool and a magazine. Since the space required for the arms to turn in is large, the multispindle head changer itself is considerably large in size.